This invention pertains to a chain saw mountable on a powered vehicle, and in particular, to such a chain saw having single-wedge-shaped chain support.
In an effort to maximize the rate at which trees are cut during timber harvesting, various devices have been constructed for the mechanical harvesting of trees. Two general approaches have been applied for solving this problem. One of them is to use devices attachable to a motor vehicle, such as a tractor, having cutting blades for slicing through a tree under hydraulic pressure. An example of such a devices is described in my prior U.S. Pat. No. 4,384,599 for "Slicing Apparatus for Felling Trees", to be issued on May 24, 1983.
Because of the forces involved in slicing there is invariably some tree fiber damage due to the compression required to force a blade laterally through a tree trunk. The solution to this problem has typically been the use of a chain saw mounted on the front of a tractor for mechanically felling trees. An approach has been to pivotally swing or transversely shift a conventional straight chain bar across an expanse in order to effect the cutting of a tree. Such a saw has substantial problems with back cutting and biting by the portion of the chain traveling on the bar over the non-cutting portion of the chain run. Additionally, when chain stretch occurs due to heat and force on the chain, the straight edges tend to produce loose chain travel. The curved ends around which such a chain travels tend to build up in heat because of the friction concentrated along those areas. This also contributes to shortened chain life.
Two types of devices have been developed in order to overcome these problems. One such device includes a wedge-shaped bar tapered on both sides toward the cutting edge for protecting the chain during the non-cutting portion of travel. A problem with this type of bar is that the lower cut surface of a tree is parallel to the direction of cut and quite immobile. The lower bar surface is forced to follow this lower tree cut surface due to the pinching action of the tree on the bar. The trailing edge of the bar therefore twists upwardly in order to accommodate this situation.
Alternatively, the width of the bar has been extremely enlarged in some cases with the intent being that the trailing edge of the chain run does not pass the edge of a tree being cut. This solution naturally requires that the diameter of trees being cut is limited to a distance less than the width of the chain bar.
It is therefore a general object of the present invention to overcome these problems of the noted prior art.
More specifically, it is a desired objective to provide a chain saw with a generally horizontal lower bar surface and an isolated trailing or non-cutting chain run.
The preferred embodiment of the present invention is a retrofit of a tree slicer made as disclosed in my above-noted U.S. patent. It comprises a chain saw mountable on a powered vehicle having a wedge-shaped chain support which tapers down to an arcuate leading edge along which a chain travels. The support has a lower generally horizontal surface and an upper surface which tapers to the leading edge. A non-cutting chain run is recessed within the support above the horizontal lower surface. The support is pivotally attached to a base plate for hydraulically forcing the same through a tree during cutting. It also has conduit means embedded in it for transmitting lubricating oil directly into the chain run during cutting.
It can be seen that such a chain saw having a wedge-shaped support tapering toward the cutting run with a horizontal lower surface provides for tree lean without twisting of the bar. Also, a chain support which essentially encloses the non-cutting chain run avoids back-cutting and biting of the chain during operation. With in-run chain lubricating, chain life is extended even further.
These and additional objects and advantages of the present invention will be more clearly understood from a consideration of the drawings and the detailed description of the preferred embodiment which follows.